Digital images are frequently sharpened after they are taken in order to reduce or remove blurriness, enhance the focus of the image, or to simulate a better resolution. Sharpening can be performed by deconvolution methods or by utilizing an unsharp mask filter to increase the contrast of edges within an image. An unsharp mask filter identifies pixels that differ from surrounding pixels by a defined threshold and increases the contrast by a specified sharpening amount. The sharpening amount can be determined and set by users, making the sharpening amount dependent on the display conditions and the visual system of the user. In other words, the sharpening amount, though a main parameter in the unsharp mask filter, is usually set according to a subjective rather than an objective determination.